Random orbital sanders are well known and typically comprise a pneumatically operated motor having a casing suitably mounted within a manually manipulated housing and a balanced, motor shaft supported for rotation relative to the motor casing by uppermost and lowermost bearings; and a motor shaft mounted bearing serving to couple the motor shaft to a sanding pad or disc.
Prior sanders of the type generally described are known to be subject to bearing failure resulting from the egress of dust particles thereinto during use. In this respect, a lowermost motor shaft support bearing is particularly subject to failure resulting from its direct exposure to a dusty or sanding environment during use and the tendency for dust ladened air to be momentarily drawn upwardly therethrough towards the interior of the motor each time the motor is turned off. The uppermost motor support bearing is known to have a substantially longer useful operating life in that it is normally shielded from dust, due to its placement wholly within the confines of the housing of the sander.
There is no known means adopted for use in sealing the lowermost motor shaft supporting bearing against the ingress of dust particles, and thus resultant failure of such bearing can severely reduce the useful operating life of a random orbital sander, particularly when used in an environment where highly abrasive dust particles are generated.
The motor shaft mounted bearing employed to couple the drive shaft to a sanding pad or disc is also know to be subject to failure due to the ingress of abrasive dust particles, and in commonly assigned U.S. Pat. No. 4,854,085 there is described a dust seal having utility with this type of bearing. However, this dust seal has the disadvantage of being of multiple part construction.